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Son Goten, Japanese pronunciation: [sõŋgotẽ̞ɴ]) is the youngest son of Goku and his wife Chi-Chi, making him a Saiyan and Earthling hybrid. Goten is Gohan's younger brother and Trunks' best friend.

Goten is the second son of Chi-Chi and Goku, and younger brother to Gohan. He is born in late Age 767, roughly nine months after the defeat of Cell in the Cell Games Saga. As Goku dies during the Cell Games, unaware Chi-Chi is pregnant, Goten does not meet his father Goku until he reaches the age of seven. Goten is not pushed in school as much as Gohan is, and instead is trained in martial arts by Chi-Chi. The reasons for this are never fully explained, but it seems to have something to do with Goku's death. Goten is incredibly strong as a child, far stronger than either Goku or Gohan ever were at his age.

In the manga, Goten transforming into a Super Saiyan made him the youngest Super Saiyan ever at that point. When Gohan asks how his transformation occurred, Goten said that he was learning Martial Arts from his mom and accidentally turned into a Super Saiyan, so she told him never to transform again. The ease at which he does so has been a matter of controversy, seeing as it took years for Goku, Vegeta, and, to a lesser extent, Gohan to obtain and master the technique. He also implies that him transforming during his training with Chi-Chi was not the first time he went Super Saiyan as he admitted he didn't remember his first time. Whatever the reason, Goten displays exceptional power at a young age, rapidly increasing his strength. During Goten's childhood he is good friends with Bulma and Vegeta's son Trunks, who he would have "fight games" with. This serves to increase their respective strength significantly, compared to the other Human-Saiyan hybrids that are seen at that age, and both became a Super Saiyan at a young age.

Power

Manga and Anime

Goten is quite powerful due to being trained by his mother and brother the first few years of his life, to the extent where he attained his Super Saiyan transformation much earlier than his brother and father. Goten's strength as a Super Saiyan was such that when he sparred with a Super Saiyan Gohan, he was able to give the latter a little trouble, with an astonished Gohan remarking just how strong the boy was. Later on, Piccolo was also taken aback at Goten and Trunks power when witnessing them turning Super Saiyan.

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Goten vs. Trunks

Compared to Trunks, Goten was slightly weaker, admitted by Goten himself and noted by Goku when he was teaching them the fusion technique and told Trunks to lower his ki a little to match Goten's. This was partly due to the fact that Trunks is one year older and naturally exhibited a little more strength as a result. After training in the Hyperbolic Time Chamber, Piccolo had stated that both he and Trunks had gained immense strength and that their power levels were exactly equal.

In Dragon Ball Super, Goten seldomly fights without Trunks at his side and they usually fuse into Gotenks. Like Trunks, Goten is kept out of the battles due to his style of charging in headfirst without thinking. While still incredibly powerful for his age his power isn't enough to face any major threat. Both Goten and Trunks stopped training but started to again after learning about the Tournament of Power. Shin mentioned and recommended Goten as a possible fighter for Universe 7 in the Tournament of Power sighting his power and young age but Goku turned him down citing he is too reckless as to is Trunks. Super Saiyan Goten was able to hold off multiple Cell Juniors at once, though he appeared to be at a disadvantage.

During the ten-year gap between the Kid Buu Saga and the 28th World Martial Arts Tournament, Goten began slacking in his disciplinary training as a result of the times of peace.[6]

In Dragon Ball GT, by the Baby Saga Goten has grown more powerful. When Baby attacks the Earth, he is strong enough to take him on, though even when Goten used a Kamehameha, he was unable to eliminate Baby - allowing the Tuffle to take over his body. Super Saiyan Baby Goten is able to fight on par with base Gohan and forces him to turn Super Saiyan by powering up and using an explosive wave. Super Saiyan Infected Gohan is at a disadvantage against base Goku and is beaten back. In the English dub, it is noted by Baby Vegeta that Uub is more powerful than the Infected Gohan, Goten and Trunks combined.

In the Super 17 Saga, in his base form, Goten is able to easily dodge Pui Pui's energy blasts and defeats him with a single kick, however he is caught off guard immediately afterward by Yakon and sweats as the Demon Beast towers over him, though he is saved by Trunks he claims he would have been able to take on Yakon by himself. Goten and Trunks together are able to destroy Android 19 by catching him off guard with a combined energy blast.

OVAs

In Dragon Ball: The Return of Son Goku and Friends!, Goten and Trunks (in their base forms) were able to take on Abo and Kado, who are on the same rank as the Ginyu Force and when arriving on Earth they are as strong as Frieza. When his and Trunks' Power Levels were read by the duo's Scouters, they each gave off a six-digit reading (while relaxed), suggesting that their battle power in base was at least 100,000.

Video games

In Dragon Ball Online, inspired by Gohan's book Groundbreaking Science, in Age 805 Goten along with his best friend Trunks became the founders of the Kikoukenjutsu Sword Style and through intense training Goten developed his natural potential as a master swordsman alongside Trunks, leading to the foundation of the Kikoukenjutsu Sword School. In Age 820, at the age of 53, both he and Trunks used their school's kenjutsu to defeat an army of Jigglers during an invasion of Earth by the remnants of the Frieza Force following the death of Mr. Satan.

Statements by authors and guidebooks

The Daizenshuu states that Goten's power was not the least bit inferior to Gohan's.[7]

In the Universe Survival Saga, Goten and Trunks were both implied, as Super Saiyans, to be stronger than Krillin and Master Roshi.

........--------------------------..........

Romeo and Juliet.

In the streets of Verona, another brawl breaks out between the servants of the feuding noble families of Capulet and Montague. Benvolio, a Montague, tries to stop the fighting, but he is himself embroiled when Tybalt, a rash Capulet, arrives on the scene. After citizens outraged by the constant violence beat back the warring factions, Prince Escalus, the ruler of Verona, attempts to prevent any further conflicts between the families by decreeing death for any individual who disturbs the peace in the future.

Romeo, the son of Montague, runs into his cousin Benvolio, who had earlier seen Romeo moping in a grove of sycamores. After some prodding by Benvolio, Romeo confides that he is in love with Rosaline, a woman who does not return his affections. Benvolio counsels him to forget this woman and find another, more beautiful one, but Romeo remains despondent.

The Ones Who Walk Away from Omelas

Meanwhile, Paris, a kinsman of the Prince, seeks Juliet's hand in marriage. Her father Capulet, though happy at the match, asks Paris to wait two years, since Juliet is not yet even fourteen. Capulet dispatches a servant with a list of people to invite to a masquerade and feast he traditionally holds. He invites Paris to the feast, hoping that Paris will begin to win Juliet's heart.

Romeo and Benvolio, still discussing Rosaline, encounter the Capulet servant bearing the list of invitations. Benvolio suggests that they attend, since that will allow Romeo to compare his beloved to other beautiful women of Verona. Romeo agrees to go with Benvolio to the feast, but only because Rosaline, whose name he reads on the list, will be there.

In Capulet's household, young Juliet talks with her mother, Lady Capulet, and her nurse about the possibility of marrying Paris. Juliet has not yet considered marriage, but agrees to look at Paris during the feast to see if she thinks she could fall in love with him.

The feast begins. A melancholy Romeo follows Benvolio and their witty friend Mercutio to Capulet's house. Once inside, Romeo sees Juliet from a distance and instantly falls in love with her; he forgets about Rosaline completely. As Romeo watches Juliet, entranced, a young Capulet, Tybalt, recognizes him, and is enraged that a Montague would sneak into a Capulet feast. He prepares to attack, but Capulet holds him back. Soon, Romeo speaks to Juliet, and the two experience a profound attraction. They kiss, not even knowing each other's names. When he finds out from Juliet's nurse that she is the daughter of Capulet—his family's enemy—he becomes distraught. When Juliet learns that the young man she has just kissed is the son of Montague, she grows equally upset.

As Mercutio and Benvolio leave the Capulet estate, Romeo leaps over the orchard wall into the garden, unable to leave Juliet behind. From his hiding place, he sees Juliet in a window above the orchard and hears her speak his name. He calls out to her, and they exchange vows of love.

Romeo hurries to see his friend and confessor Friar Lawrence, who, though shocked at the sudden turn of Romeo's heart, agrees to marry the young lovers in secret since he sees in their love the possibility of ending the age-old feud between Capulet and Montague. The following day, Romeo and Juliet meet at Friar Lawrence's cell and are married. The Nurse, who is privy to the secret, procures a ladder, which Romeo will use to climb into Juliet's window for their wedding night.

The next day, Benvolio and Mercutio encounter Tybalt—Juliet's cousin—who, still enraged that Romeo attended Capulet's feast, has challenged Romeo to a duel. Romeo appears. Now Tybalt's kinsman by marriage, Romeo begs the Capulet to hold off the duel until he understands why Romeo does not want to fight. Disgusted with this plea for peace, Mercutio says that he will fight Tybalt himself. The two begin to duel. Romeo tries to stop them by leaping between the combatants. Tybalt stabs Mercutio under Romeo's arm, and Mercutio dies. Romeo, in a rage, kills Tybalt. Romeo flees from the scene. Soon after, the Prince declares him forever banished from Verona for his crime. Friar Lawrence arranges for Romeo to spend his wedding night with Juliet before he has to leave for Mantua the following morning.

In her room, Juliet awaits the arrival of her new husband. The Nurse enters, and, after some confusion, tells Juliet that Romeo has killed Tybalt. Distraught, Juliet suddenly finds herself married to a man who has killed her kinsman. But she resettles herself, and realizes that her duty belongs with her love: to Romeo.

Romeo sneaks into Juliet's room that night, and at last they consummate their marriage and their love. Morning comes, and the lovers bid farewell, unsure when they will see each other again. Juliet learns that her father, affected by the recent events, now intends for her to marry Paris in just three days. Unsure of how to proceed—unable to reveal to her parents that she is married to Romeo, but unwilling to marry Paris now that she is Romeo's wife—Juliet asks her nurse for advice. She counsels Juliet to proceed as if Romeo were dead and to marry Paris, who is a better match anyway. Disgusted with the Nurse's disloyalty, Juliet disregards her advice and hurries to Friar Lawrence. He concocts a plan to reunite Juliet with Romeo in Mantua. The night before her wedding to Paris, Juliet must drink a potion that will make her appear to be dead. After she is laid to rest in the family's crypt, the Friar and Romeo will secretly retrieve her, and she will be free to live with Romeo, away from their parents' feuding.

Juliet returns home to discover the wedding has been moved ahead one day, and she is to be married tomorrow. That night, Juliet drinks the potion, and the Nurse discovers her, apparently dead, the next morning. The Capulets grieve, and Juliet is entombed according to plan. But Friar Lawrence's message explaining the plan to Romeo never reaches Mantua. Its bearer, Friar John, gets confined to a quarantined house. Romeo hears only that Juliet is dead.

Romeo learns only of Juliet's death and decides to kill himself rather than live without her. He buys a vial of poison from a reluctant Apothecary, then speeds back to Verona to take his own life at Juliet's tomb. Outside the Capulet crypt, Romeo comes upon Paris, who is scattering flowers on Juliet's grave. They fight, and Romeo kills Paris. He enters the tomb, sees Juliet's inanimate body, drinks the poison, and dies by her side. Just then, Friar Lawrence enters and realizes that Romeo has killed Paris and himself. At the same time, Juliet awakes. Friar Lawrence hears the coming of the watch. When Juliet refuses to leave with him, he flees alone. Juliet sees her beloved Romeo and realizes he has killed himself with poison. She kisses his poisoned lips, and when that does not kill her, buries his dagger in her chest, falling dead upon his body.

The watch arrives, followed closely by the Prince, the Capulets, and Montague. Montague declares that Lady Montague has died of grief over Romeo's exile. Seeing their children's bodies, Capulet and Montague agree to end their long-standing feud and to raise gold statues of their children side-by-side in a newly peaceful Verona.

--------------A brief history of dinosaurs-------------

Dinosaurs were a successful group of animals that emerged between 240 million and 230 million years ago and came to rule the world until about 66 million years ago, when a giant asteroid slammed into Earth. During that time, dinosaurs evolved from a group of mostly dog- and horse-size creatures into the most enormous beasts that ever existed on land.

Some meat-eating dinosaurs shrank over time and evolved into birds. So, in that sense, only the non-avian dinosaurs went extinct. (For the purposes of this article, "dinosaurs" will refer to non-avian dinosaurs, unless otherwise stated.)

During the roughly 174 million years that dinosaurs existed, the world changed greatly. When dinosaurs first appeared in the Triassic period (251.9 million to 201.3 million years ago), they roamed the supercontinent of Pangaea. But by the time the asteroid hit at the end of the Cretaceous period (145 million to 66 million years ago), the continents were in approximately the same place they are today.

WHAT ARE DINOSAURS?

The oldest unequivocal dinosaur fossils, dating to about 231 million years ago, are from Ischigualasto Provincial Park in northwestern Argentina, and include the genuses Herrerasaurus, Eoraptor and Eodromaeus. Scientists are still debating whether Nyasasaurus, a genus found in Tanzania that dates to about 240 million years ago, is also an early dinosaur or a dinosauromorph, a group that includes dinosaurs and their close relatives, said Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland.

Related: Photos: Unearthing dinosauromorphs, the ancestors of dinosaurs

Whenever they first appeared, the dinosaurs' unique anatomy set them apart from other animal groups. Dinosaurs are archosaurs, a clade (different groups of animals that share a common ancestor) that includes crocodilians, pterosaurs, dinosaurs and birds. The archosaurs emerged after the end-Permian extinction about 252 million years ago. Over time, some archosaurs, including dinosauromorphs, adapted an upright posture, meaning they had legs under their bodies, rather than out to their sides.

"Sprawling is all well and good for cold-blooded critters that don't need to move very fast. Tucking your limbs under your body, however, opens up a new world of possibilities," Brusatte wrote in "The Rise and Fall of the Dinosaurs: A New History of a Lost World" (William Morrow, 2018). As archosaur evolution progressed, dinosauromorphs gained long tails, big leg muscles and extra hip bones that enabled them to move quickly and efficiently, Brusatte wrote.

Photo of a Tyrannosaurus rex skeleton on display at a museum.

Dinosaurs were likely warm blooded. Their unique anatomy, such as their strong necks and upright posture, gave them advantages over other animal groups. (Image credit: UNM Biology)

Some dinosauromorphs evolved into dinosaurs. The differences between the two are small, but dinosaurs' anatomy offered increased benefits, including arms that could move in and out, neck vertebrae that could support stronger muscles than before, and a joint where the thigh bone meets the pelvis, Brusatte wrote.

This unique anatomy helped dinosaurs become successful. Having an upright posture also freed the hands, allowing dinosaurs such as iguanodonts to grasp branches and carnivorous dinosaurs to claw and kill prey, noted Gregory Erickson, a paleobiologist at Florida State University. Ultimately, having free arms "allowed gliding then flight in birds," he said.

Moreover, dinosaurs were likely warm blooded, according to research on their growth rates. "When you become a warm blooded animal, you can operate 24/7," Erickson told Live Science. "You're not at the whims of the environment in terms of being active."

Initially, dinosaurs were not as diverse as the crocodile-like archosaurs they were living alongside, Brusatte noted. In fact, dinosaurs "didn't become too successful right away; the crocs ruled the Triassic, then the end-Triassic extinction hit and the dinosaurs survived and took over."

The clade Dinosauria (which means "terrible lizard" in Greek) was coined in 1842 by the English paleontologist Richard Owen, who included the meat-eating theropod Megalosaurus, the long-necked sauropodomorph Cetiosaurus and the ornithiscian Iguanodon as the first known species in the clade, according to the book "Dinosaurs Rediscovered" (Thames & Hudson, 2019).

Each of these dinosaurs, it turns out, represents one of the three major dinosaur groups.

TYPES OF DINOSAURS

As of 2021, there were 1,545 scientifically described dinosaur species, according to the Paleobiology Database. About 50 previously unknown species are described each year, meaning there's roughly one newfound species described each week, Brusatte said.

All of these dinosaurs fit into one of three groups: Ornithischia, Sauropodomorpha and Theropoda.

Ornithischia dinosaurs include beaked plant-eaters, such as Stegosaurus, duck-billed dinosaurs (also called hadrosaurs), as well as horned dinosaurs like Triceratops and armored dinosaurs like Ankylosaurus. Some ornithischians walked on four legs, while others walked on two.

Sauropodomorpha dinosaurs were long-necked, pot-bellied dinosaurs that had tiny heads and column-like limbs. This group includes sauropods (such as Diplodocus), their smaller antecedents (including Chromogisaurus) and extra-large sauropods known as titanosaurs (such as Dreadnoughtus and Argentinosaurus), which are among the largest land animals that have ever existed.

A life-scene from 232 million years ago, during the Carnian Pluvial Episode after which dinosaurs took over. A large rauisuchian lurks in the background, while two species of dinosaurs stand in the foreground, and some rhynchosaurs sit on the logs to the left. Based on data from the Ischigualasto Formation in Argentina.

A life-scene from 232 million years ago, during the Carnian Pluvial Episode after which dinosaurs took over. A large archosaur, known as a rauisuchian, lurks in the background, while two species of dinosaurs stand in the foreground, and some rhynchosaurs sit on the logs to the left. Based on data from the Ischigualasto Formation in Argentina. (Image credit: © Davide Bonadonna)

Theropoda is a group of meat-eating dinosaurs, although some (such as Chilesaurus diegosuarezi) changed their diet to be herbivorous or omnivorous. Theropods include Tyrannosaurus rex and Velociraptor, as well as birds, which evolved from small theropods.

So, how are these groups related? It's up for debate. Ornithischian dinosaurs have a backward-pointing pubis bone in the hip, earning them the name bird-hipped dinosaurs. (However, they are not the ancestors of birds; theropods are.) Meanwhile, theropods and sauropodomorphs have saurischian or "reptile hips," which are also seen in modern crocodiles and lizards, according to the book "Dinosaurs Rediscovered."

Historically, it was thought that the reptile-hipped theropods and sauropodomorphs were more closely related to each other than to ornithischians. However, a 2017 study in the journal Nature uprooted the dinosaur family tree by suggesting that ornithischians and theropods were more closely related, based on analyses of 74 dinosaur species, Live Science previously reported. Shortly after, another 2017 study in the journal Nature found that neither family tree, as well as a third that is rarely considered, is statistically significant from the other, meaning all the suggested family trees are equally plausible until more evidence comes forth.

WHEN DID DINOSAURS LIVE?

Dinosaurs lived during most of the Mesozoic era, a geological age that lasted from 252 million to 66 million years ago. The Mesozoic era includes the Triassic, Jurassic and Cretaceous periods.

Dinosaurs arose from small dinosauromorph ancestors in the Triassic period, when the climate was harsh and dry. They faced "competition from the croc-line archosaurs for tens of millions of years, [but] finally prevailed when Pangaea began to split," Brusatte told Live Science. At this time, volcanoes erupted along the cracks of the supercontinent, causing global warming and mass extinction, he said.

During the Jurassic period (201.3 million to 145 million years ago), dinosaurs rose to dominance and some grew to huge sizes. For example, Vouivria damparisensis, the earliest titanosaur, dates to 160 million years ago. It weighed about 33,000 lbs. (15,000 kilograms) and measured more than 50 feet (15 meters) long. Iconic dinosaurs from this period include Brontosaurus, Brachiosaurus, Diplodocus and Stegosaurus. During the Jurassic, flowering plants evolved and birds, including Archaeopteryx, first appeared. There was "a small extinction at the end of the Jurassic that we still know little about," Brusatte said.

In the Cretaceous period, dinosaur dominance continued as the continents moved farther apart. Famous dinosaurs from this period include T. rex, Triceratops, Spinosaurus and Velociraptor. The largest dinosaurs on record, including Argentinosaurus, date to the Cretaceous. The Cretaceous period ended with the Cretaceous-Tertiary (K-Pg) extinction event, when a 6-mile-wide (10 kilometers) asteroid collided with Earth, leaving an impact crater more than 110 miles (180 km) in diameter in the Yucatan Peninsula of what is now Mexico.

The impact area, known as the Chicxulub (CHEEK-sheh-loob) crater, has evidence of "shocked quartz" and small glass-like spheres known as tektites, which form when rock is rapidly vaporized and cooled — geologic clues that a space rock struck there with incredible force, Betsy Kruk, an associate paleontologist with Paleo Solutions, a paleontological consulting company based in California, previously told Live Science. Chemical analyses from the sedimentary rock at Chicxulub melted and mixed together at temperatures on par with an asteroid strike about 66 million years ago, she added.

WHAT IS THE LARGEST DINOSAUR? THE SMALLEST DINOSAUR?

Some dinosaurs were enormous, but others were pipsqueaks. The smallest dinosaur on record is an avian dinosaur that's alive today: the bee hummingbird (Mellisuga helenae) from Cuba, which measures just over 2 inches (5 centimeters) long and weighs less than 0.07 ounce (2 grams). As for extinct, non-avian dinosaurs, there are a few contenders for smallest beast, including a bat-like dinosaur from China named Ambopteryx longibrachium that measured 13 inches (32 cm) long and weighed about 11 oz (306 g), according to a 2019 study in the journal Nature.

Titanosaurs were the largest dinosaurs. However, because paleontologists rarely find an entire skeleton, and because soft tissues, such as organs and muscles, rarely fossilize, it's challenging to determine dinosaur mass. However, contenders for the title of world's largest dinosaur include Argentinosaurus, which weighed up to 110 tons (100 metric tons), an unnamed 98 million-year-old titanosaur from Argentina that weighed upward of 69 tons (63 metric tons), and Patagotitan, which also weighed in at 69 tons.

The longest dinosaur was likely Supersaurus, a Jurassic sauropod that was at least 128 feet (39 meters) long, and possibly even reached 137 feet (42 m) in length, according to unpublished research presented at the Society of Vertebrate Paleontology's annual conference in 2021. Another contender is Diplodocus, a long and slender Jurassic sauropod that could reach lengths of 108 feet (33 m), according to a 2006 study in the New Mexico Museum of Natural History and Science Bulletin.

The tallest dinosaur is likely Giraffatitan, a 40-foot-tall (12 m) sauropod dinosaur from the late Jurassic, about 150 million years ago, which lived in what is now Tanzania.

PTEROSAURS ARE NOT DINOSAURS

Many amazing animals lived during the dinosaur age, and some are confused with dinosaurs. The most common misconception is calling pterosaurs dinosaurs: They are not. Pterosaurs are winged reptiles and archosaurs, meaning they are relatives of dinosaurs, but they are not dinosaurs.

The order Crocodilia includes extinct and living crocodiles and their close relatives. Crocodilians are archosaurs, but they are not dinosaurs. Living crocodilians and birds (which are dinosaurs) are the only surviving members of the Archosauria clade.

The Mesozoic oceans teemed with sea life, including predatory reptiles known as mosasaurs (such as Mosasaurus), plesiosaurs and ichthyosaurs. However, none of these reptiles are dinosaurs.

DID DINOSAURS HAVE FEATHERS?

Yes, some dinosaurs flaunted feathers, as do their bird descendants. Feathers don't fossilize well, but some remarkable fossils, especially those from Liaoning province in China that were buried in the aftermath of a volcanic eruption, have preserved feathers. Here are a few examples: Zhenyuanlong suni, Yutyrannus huali and Jianianhualong tengi.

It's unclear why dinosaurs first evolved feathers, but they could have been used for the following: as insulation to keep dinosaurs and their incubated eggs warm; for display to use for communication between dinosaurs, such as courtship displays; and for gliding or powered flight, Michael Habib, a research associate at the Dinosaur Institute at the Natural History Museum of Los Angeles County, previously told Live Science.

Initially, it was thought that only theropods and their descendants sported feathers, but researchers have also found downy feathers on the plant-eating ornithischian dinosaur Kulindadromeus zabaikalicus, suggesting that feathers were more widespread than previously thought, a 2014 study in the journal Science found.

Artist's depiction of Theropod cannibals in a stressed Late Jurassic ecosystem.

Theropod cannibals in a stressed late Jurassic ecosystem. (Image credit: Brian Engh )

It's possible that pterosaurs had feathers, according to a 2018 study in the journal Nature Ecology & Evolution, but more feathered specimens need to be found and analyzed to say so for sure.

Notably, even T. rex had feathers. However, depictions of dinosaurs rarely have feathers in popular culture, including the "Jurassic Park" movies. Paleontologist Jack Horner, who served as a scientific adviser on some of the "Jurassic Park" movies, remembers telling director Steven Spielberg that the dinosaurs should have feathers.

"Even when 'Jurassic Park' came out [in 1993], we knew that Velociraptors should have feathers, but at that time, it would have been technically difficult to do it, just from a CG [computer-generated] point of view. And Steven wasn't really too excited about it, anyway. When I told him they should be colorful and they should be feathered, and he said, 'Feathered Technicolor dinosaurs aren't scary enough,'" Horner previously told Live Science.

COULD DINOSAURS FLY?

Some dinosaurs could fly, including the earliest known bird — Archaeopteryx — discovered in Germany and dating to about 150 million years ago, during the late Jurassic.

However, unlike most birds today, extinct dinosaurs likely just flew short distances. Research shows that powerful leg muscles, big wings and a relatively small body size were needed for takeoff and flight in ancient birds and bird-like dinosaurs, Habib previously told Live Science. His research suggests that the bird-like dinosaurs Microraptor, Rahonavis, and five avian genuses — Archaeopteryx, Sapeornis, Jeholornis, Eoconfuciusornis and Confuciusornis — would have been able to launch (without running) from the ground to initiate flight.

The bat-like dinosaur Yi qi, dating to China's Jurassic period, had wings, according to a 2015 study in the journal Nature. However, it likely didn't have powered flight and was probably a terrible glider, a 2020 study in the journal iScience found.

This is an artist's impression of Zhenyuanlong suni, a winged dinosaur that's a close cousin of the Velociraptor. Despite having bird-like wings, it probably could not fly, at least not using the same type of powerful muscle-driven flight as modern birds, researchers say.

This is an artist's impression of Zhenyuanlong suni, a winged dinosaur that's a close cousin of the Velociraptor. Despite having bird-like wings, it probably could not fly, at least not using the same type of powerful muscle-driven flight as modern birds, researchers say. (Image credit: Chuang Zhao)

WHY DID DINOSAURS GO EXTINCT?

It's up for debate how well the dinosaurs were doing before the asteroid crashed into Earth. A handful of studies suggest that in the late Cretaceous, dinosaur extinctions were rising and diversity was declining, especially among herbivorous dinosaurs. But these studies rely on incomplete fossil data and models that may not tell the whole story, Live Science previously reported.

Even if dinosaur diversity was dropping, it's possible they could have bounced back had the asteroid not hit, Brusatte told Live Science. Dinosaurs lived on every continent, including Antarctica, and they filled different rungs in various ecosystems, from plant-eater to apex carnivore. "Dinosaurs had experienced many rises and falls in diversity over their 150-plus million year evolutionary history," he said. If the mass extinction hadn't happened, it's possible "They would still be thriving today as more than birds."

In the aftermath of the asteroid collision, long-term pain followed chaos. The collision caused massive destruction, including a shockwave, heat pulse, wildfires, tsunamis (including an immediate mile-high tsunami), volcanic eruptions, lethal acid rain and earthquakes. Dust and grime that the asteroid kicked up hovered in the air. "This rain of hot dust raised global temperatures for hours after the impact, and cooked alive animals that were too large to seek shelter," according to Kruk. "Small animals that could shelter underground, underwater, or perhaps in caves or large tree trunks, may have been able to survive this initial heat blast."

The dust and particles remained in the air, blocking the sun for several years afterward and causing a nuclear winter that cooled the planet and led to the deaths of countless plants and animals, Brusatte and Kruk said.

"Smaller, omnivorous terrestrial animals, like mammals, lizards, turtles, or birds, may have been able to survive as scavengers feeding on the carcasses of dead dinosaurs, fungi, roots and decaying plant matter, while smaller animals with lower metabolisms were best able to wait the disaster out," Kruk previously said. Moreover, the asteroid also pulverized carbon-rich rocks, which released carbon into the atmosphere and led to "global warming for a few thousand years," after the nuclear winter ended, Brusatte said.

Scientists used to wonder if the Deccan Traps volcanic eruptions in what is now India played a role in the mass extinction. But recent studies "show that the Deccan probably had very little impact," Brusatte said. It was "most likely an innocent bystander" — the asteroid is what caused the extinction.

CAN DINOSAURS BE BROUGHT BACK?

In the popular movie franchise "Jurassic Park," scientists find dinosaur DNA preserved in an ancient mosquito caught in amber, and then fill in the DNA gaps with frog DNA. It's an entertaining plot, but the science is far from sound. For instance, amber does not preserve DNA well, and frogs are not at all closely related to dinosaurs; they're not archosaurs, and a 2017 study in the journal Proceedings of the National Academy of Sciences even found that frog evolution took off after the asteroid impact.

For myriad reasons, it's currently impossible to bring extinct dinosaurs back. While dinosaur proteins and blood vessels have been found, scientists have yet to rigorously identify DNA from an extinct dinosaur. DNA begins decaying the moment an organism dies, but parts of it can be preserved in the right circumstances. That said, the oldest sequenced DNA on record belongs to a roughly 1 million-year-old mammoth, and dinosaurs went extinct about 66 million years ago.

Some scientists are studying how to reverse-engineer birds into dinosaurs, including the so-called "dino-chicken," which would have a lengthened tail, teeth, arms and fingers. One group even gave chicken embryos dinosaur-like snouts. However, the "chickenosaurus" wouldn't be a replica of an ancient dinosaur, but rather a dinosaur-like bird, the researchers told Live Science.

------Geological history of Earth------------

Precambrian

Main article: Precambrian

The Precambrian includes approximately 90% of geologic time. It extends from 4.6 billion years ago to the beginning of the Cambrian Period (about 539 Ma). It includes the first three of the four eons of Earth's prehistory (the Hadean, Archean and Proterozoic) and precedes the Phanerozoic eon.[5]

Major volcanic events altering the Earth's environment and causing extinctions may have occurred 10 times in the past 3 billion years.[6]

Hadean Eon

Main article: Hadean

Artist's conception of a protoplanetary disc

During Hadean time (4.6–4 Ga), the Solar System was forming, probably within a large cloud of gas and dust around the sun, called an accretion disc from which Earth formed 4,500 million years ago.[7] The Hadean Eon is not formally recognized, but it essentially marks the era before we have adequate record of significant solid rocks. The oldest dated zircons date from about 4,400 million years ago.[8][9][10]

Artist's impression of a Hadean landscape and the Moon looming large in the sky, both bodies still under extreme volcanism.

Earth was initially molten due to extreme volcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed soon afterwards, possibly as a result of the impact of a large planetoid with the Earth.[11][12] More recent potassium isotopic studies suggest that the Moon was formed by a smaller, high-energy, high-angular-momentum giant impact cleaving off a significant portion of the Earth.[13] Some of this object's mass merged with the Earth, significantly altering its internal composition, and a portion was ejected into space. Some of the material survived to form an orbiting moon. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice delivered from comets, produced the oceans.[14] However, in 2020, researchers reported that sufficient water to fill the oceans may have always been on the Earth since the beginning of the planet's formation.[1][2][3]

During the Hadean the Late Heavy Bombardment occurred (approximately 4,100 to 3,800 million years ago) during which a large number of impact craters are believed to have formed on the Moon, and by inference on Earth, Mercury, Venus and Mars as well. However, some scientists argue against this hypothetical Late Heavy Bombardment, pointing that the this conclusion has been drawn from data which are not fully representative (only a few crater hotspots on the Moon have been analyzed).[15][16]

Archean Eon

Main article: Archean

Artist's impression of Earth during its second eon, the Archean. The eon started with the Late Heavy Bombardment around 4 billion years ago. As depicted, Earth's planetary crust had largely cooled, leaving a water-rich barren surface marked by volcanoes and continents, eventually developing round microbialites. The Moon orbited Earth much closer, appearing much larger, producing more frequent and wider eclipses as well as tidal effects.[17]

The Earth of the early Archean (4,000 to 2,500 million years ago) may have had a different tectonic style. During this time, the Earth's crust cooled enough that rocks and continental plates began to form. Some scientists think because the Earth was hotter, that plate tectonic activity was more vigorous than it is today, resulting in a much greater rate of recycling of crustal material. This may have prevented cratonization and continent formation until the mantle cooled and convection slowed down. Others argue that the subcontinental lithospheric mantle is too buoyant to subduct and that the lack of Archean rocks is a function of erosion and subsequent tectonic events. Some geologists view the sudden increase of aluminum content in zircons as an indicator of the beginning of plate tectonics.[18]

In contrast to the Proterozoic, Archean rocks are often heavily metamorphized deep-water sediments, such as graywackes, mudstones, volcanic sediments and banded iron formations. Greenstone belts are typical Archean formations, consisting of alternating high- and low-grade metamorphic rocks. The high-grade rocks were derived from volcanic island arcs, while the low-grade metamorphic rocks represent deep-sea sediments eroded from the neighboring island rocks and deposited in a forearc basin. In short, greenstone belts represent sutured protocontinents.[19]

The Earth's magnetic field was established 3.5 billion years ago. The solar wind flux was about 100 times the value of the modern Sun, so the presence of the magnetic field helped prevent the planet's atmosphere from being stripped away, which is what probably happened to the atmosphere of Mars. However, the field strength was lower than at present and the magnetosphere was about half the modern radius.[20]

Proterozoic Eon

Main article: Proterozoic

The geologic record of the Proterozoic (2,500 to 539 million years ago[21]) is more complete than that for the preceding Archean. In contrast to the deep-water deposits of the Archean, the Proterozoic features many strata that were laid down in extensive shallow epicontinental seas; furthermore, many of these rocks are less metamorphosed than Archean-age ones, and plenty are unaltered.[22] Study of these rocks show that the eon featured massive, rapid continental accretion (unique to the Proterozoic), supercontinent cycles, and wholly modern orogenic activity.[23] Roughly 750 million years ago,[24] the earliest-known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia, 600–540 Ma.[9][25]

The first-known glaciations occurred during the Proterozoic, one began shortly after the beginning of the eon, while there were at least four during the Neoproterozoic, climaxing with the Snowball Earth of the Varangian glaciation.[26]

Artist's rendition of a oxinated fully-frozen Snowball Earth with no remaining liquid surface water.

Phanerozoic

Main article: Phanerozoic

The Phanerozoic Eon is the current eon in the geologic timescale. It covers roughly 539 million years. During this period continents drifted apart, but eventually collected into a single landmass known as Pangea, before splitting again into the current continental landmasses.

The Phanerozoic is divided into three eras – the Paleozoic, the Mesozoic and the Cenozoic.

Most of the evolution of multicellular life occurred during this time period.

Paleozoic Era

Main article: Paleozoic

The Paleozoic spanned from roughly 539 to 251 million years ago (Ma)[27] and is subdivided into six geologic periods; from oldest to youngest they are the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. Geologically, the Paleozoic starts shortly after the breakup of a supercontinent called Pannotia and at the end of a global ice age. Throughout the early Paleozoic, the Earth's landmass was broken up into a substantial number of relatively small continents. Toward the end of the era the continents gathered together into a supercontinent called Pangaea, which included most of the Earth's land area.

Cambrian Period

Main article: Cambrian

The Cambrian is a major division of the geologic timescale that begins about 538.8 ± 0.2 Ma.[28] Cambrian continents are thought to have resulted from the breakup of a Neoproterozoic supercontinent called Pannotia. The waters of the Cambrian period appear to have been widespread and shallow. Continental drift rates may have been anomalously high. Laurentia, Baltica and Siberia remained independent continents following the break-up of the supercontinent of Pannotia. Gondwana started to drift toward the South Pole. Panthalassa covered most of the southern hemisphere, and minor oceans included the Proto-Tethys Ocean, Iapetus Ocean and Khanty Ocean.

Ordovician period

Main article: Ordovician

The Ordovician period started at a major extinction event called the Cambrian–Ordovician extinction event some time about 485.4 ± 1.9 Ma.[9] During the Ordovician the southern continents were collected into a single continent called Gondwana. Gondwana started the period in the equatorial latitudes and, as the period progressed, drifted toward the South Pole. Early in the Ordovician the continents Laurentia, Siberia and Baltica were still independent continents (since the break-up of the supercontinent Pannotia earlier), but Baltica began to move toward Laurentia later in the period, causing the Iapetus Ocean to shrink between them. Also, Avalonia broke free from Gondwana and began to head north toward Laurentia. The Rheic Ocean was formed as a result of this. By the end of the period, Gondwana had neared or approached the pole and was largely glaciated.

The Ordovician came to a close in a series of extinction events that, taken together, comprise the second-largest of the five major extinction events in Earth's history in terms of percentage of genera that became extinct. The only larger one was the Permian-Triassic extinction event. The extinctions occurred approximately 447 to 444 million years ago [9] and mark the boundary between the Ordovician and the following Silurian Period.

The most-commonly accepted theory is that these events were triggered by the onset of an ice age, in the Hirnantian faunal stage that ended the long, stable greenhouse conditions typical of the Ordovician. The ice age was probably not as long-lasting as once thought; study of oxygen isotopes in fossil brachiopods shows that it was probably no longer than 0.5 to 1.5 million years.[29] The event was preceded by a fall in atmospheric carbon dioxide (from 7000ppm to 4400ppm) which selectively affected the shallow seas where most organisms lived. As the southern supercontinent Gondwana drifted over the South Pole, ice caps formed on it. Evidence of these ice caps have been detected in Upper Ordovician rock strata of North Africa and then-adjacent northeastern South America, which were south-polar locations at the time.

Silurian Period

Main article: Silurian

The Silurian is a major division of the geologic timescale that started about 443.8 ± 1.5 Ma.[9] During the Silurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian ice caps were less extensive than those of the late Ordovician glaciation. The melting of ice caps and glaciers contributed to a rise in sea levels, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. Other cratons and continent fragments drifted together near the equator, starting the formation of a second supercontinent known as Euramerica. The vast ocean of Panthalassa covered most of the northern hemisphere. Other minor oceans include Proto-Tethys, Paleo-Tethys, Rheic Ocean, a seaway of Iapetus Ocean (now in between Avalonia and Laurentia), and newly formed Ural Ocean.

Devonian Period

Main article: Devonian

The Devonian spanned roughly from 419 to 359 Ma.[9] The period was a time of great tectonic activity, as Laurasia and Gondwana drew closer together. The continent Euramerica (or Laurussia) was created in the early Devonian by the collision of Laurentia and Baltica, which rotated into the natural dry zone along the Tropic of Capricorn. In these near-deserts, the Old Red Sandstone sedimentary beds formed, made red by the oxidized iron (hematite) characteristic of drought conditions. Near the equator Pangaea began to consolidate from the plates containing North America and Europe, further raising the northern Appalachian Mountains and forming the Caledonian Mountains in Great Britain and Scandinavia. The southern continents remained tied together in the supercontinent of Gondwana. The remainder of modern Eurasia lay in the Northern Hemisphere. Sea levels were high worldwide, and much of the land lay submerged under shallow seas. The deep, enormous Panthalassa (the "universal ocean") covered the rest of the planet. Other minor oceans were Paleo-Tethys, Proto-Tethys, Rheic Ocean and Ural Ocean (which was closed during the collision with Siberia and Baltica).

Carboniferous Period

Main article: Carboniferous

The Carboniferous extends from about 358.9 ± 0.4 to about 298.9 ± 0.15 Ma.[9]

A global drop in sea level at the end of the Devonian reversed early in the Carboniferous; this created the widespread epicontinental seas and carbonate deposition of the Mississippian. There was also a drop in south polar temperatures; southern Gondwana was glaciated throughout the period, though it is uncertain if the ice sheets were a holdover from the Devonian or not. These conditions apparently had little effect in the deep tropics, where lush coal swamps flourished within 30 degrees of the northernmost glaciers. A mid-Carboniferous drop in sea-level precipitated a major marine extinction, one that hit crinoids and ammonites especially hard. This sea-level drop and the associated unconformity in North America separate the Mississippian Period from the Pennsylvanian period.[30]

The Carboniferous was a time of active mountain building, as the supercontinent Pangea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America-Europe (Laurussia) along the present line of eastern North America. This continental collision resulted in the Hercynian orogeny in Europe, and the Alleghenian orogeny in North America; it also extended the newly uplifted Appalachians southwestward as the Ouachita Mountains.[31] In the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. There were two major oceans in the Carboniferous: the Panthalassa and Paleo-Tethys. Other minor oceans were shrinking and eventually closed the Rheic Ocean (closed by the assembly of South and North America), the small, shallow Ural Ocean (which was closed by the collision of Baltica, and Siberia continents, creating the Ural Mountains) and Proto-Tethys Ocean.

Pangaea separation animation

Permian Period

Main article: Permian

The Permian extends from about 298.9 ± 0.15 to 252.17 ± 0.06 Ma.[9]

During the Permian all the Earth's major land masses, except portions of East Asia, were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean (Panthalassa, the universal sea), and the Paleo-Tethys Ocean, a large ocean that was between Asia and Gondwana. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmasses create climates with extreme variations of heat and cold ("continental climate") and monsoon conditions with highly seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea.

Mesozoic Era

Main article: Mesozoic

Plate tectonics - 249 million years ago

Plate tectonics - 290 million years ago

The Mesozoic extended roughly from 252 to 66 million years ago.[9]

After the vigorous convergent plate mountain-building of the late Paleozoic, Mesozoic tectonic deformation was comparatively mild. Nevertheless, the era featured the dramatic rifting of the supercontinent Pangaea. Pangaea gradually split into a northern continent, Laurasia, and a southern continent, Gondwana. This created the passive continental margin that characterizes most of the Atlantic coastline (such as along the U.S. East Coast) today.

Triassic Period

Main article: Triassic

The Triassic Period extends from about 252.17 ± 0.06 to 201.3 ± 0.2 Ma.[9] During the Triassic, almost all the Earth's land mass was concentrated into a single supercontinent centered more or less on the equator, called Pangaea ("all the land"). This took the form of a giant "Pac-Man" with an east-facing "mouth" constituting the Tethys sea, a vast gulf that opened farther westward in the mid-Triassic, at the expense of the shrinking Paleo-Tethys Ocean, an ocean that existed during the Paleozoic.

The remainder was the world-ocean known as Panthalassa ("all the sea"). All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates; thus, very little is known of the Triassic open ocean. The supercontinent Pangaea was rifting during the Triassic—especially late in the period—but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangea—which separated New Jersey from Morocco—are of Late Triassic age; in the U.S., these thick sediments comprise the Newark Supergroup.[32] Because of the limited shoreline of one super-continental mass, Triassic marine deposits are globally relatively rare; despite their prominence in Western Europe, where the Triassic was first studied. In North America, for example, marine deposits are limited to a few exposures in the west. Thus Triassic stratigraphy is mostly based on organisms living in lagoons and hypersaline environments, such as Estheria crustaceans and terrestrial vertebrates.[33]

Jurassic Period

Main article: Jurassic

The Jurassic Period extends from about 201.3 ± 0.2 to 145.0 Ma.[9] During the early Jurassic, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Gulf of Mexico opened in the new rift between North America and what is now Mexico's Yucatan Peninsula. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous Period, when Gondwana itself rifted apart.[34] The Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of glaciation. As in the Triassic, there was apparently no land near either pole, and no extensive ice caps existed. The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of the continent was submerged under shallow tropical seas; famous locales include the Jurassic Coast World Heritage Site and the renowned late Jurassic lagerstätten of Holzmaden and Solnhofen.[35] In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface.[36] Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation. The first of several massive batholiths were emplaced in the northern Cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny.[37] Important Jurassic exposures are also found in Russia, India, South America, Japan, Australasia and the United Kingdom.

Cretaceous Period

Main article: Cretaceous

Plate tectonics - 100 Ma,[9] Cretaceous period

The Cretaceous Period extends from circa 145 million years ago to 66 million years ago.[9]

During the Cretaceous, the late Paleozoic-early Mesozoic supercontinent of Pangaea completed its breakup into present day continents, although their positions were substantially different at the time. As the Atlantic Ocean widened, the convergent-margin orogenies that had begun during the Jurassic continued in the North American Cordillera, as the Nevadan orogeny was followed by the Sevier and Laramide orogenies. Though Gondwana was still intact in the beginning of the Cretaceous, Gondwana itself broke up as South America, Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached to each other); thus, the South Atlantic and Indian Oceans were newly formed. Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels worldwide.

To the north of Africa the Tethys Sea continued to narrow. Broad shallow seas advanced across central North America (the Western Interior Seaway) and Europe, then receded late in the period, leaving thick marine deposits sandwiched between coal beds. At the peak of the Cretaceous transgression, one-third of Earth's present land area was submerged.[38] The Cretaceous is justly famous for its chalk; indeed, more chalk formed in the Cretaceous than in any other period in the Phanerozoic.[39] Mid-ocean ridge activity—or rather, the circulation of seawater through the enlarged ridges—enriched the oceans in calcium; this made the oceans more saturated, as well as increased the bioavailability of the element for calcareous nanoplankton.[40] These widespread carbonates and other sedimentary deposits make the Cretaceous rock record especially fine. Famous formations from North America include the rich marine fossils of Kansas's Smoky Hill Chalk Member and the terrestrial fauna of the late Cretaceous Hell Creek Formation. Other important Cretaceous exposures occur in Europe and China. In the area that is now India, massive lava beds called the Deccan Traps were laid down in the very late Cretaceous and early Paleocene.

Cenozoic Era

Main article: Cenozoic

The Cenozoic Era covers the 66 million years since the Cretaceous–Paleogene extinction event up to and including the present day. By the end of the Mesozoic era, the continents had rifted into nearly their present form. Laurasia became North America and Eurasia, while Gondwana split into South America, Africa, Australia, Antarctica and the Indian subcontinent, which collided with the Asian plate. This impact gave rise to the Himalayas. The Tethys Sea, which had separated the northern continents from Africa and India, began to close up, forming the Mediterranean Sea.

Paleogene Period

Main article: Paleogene

The Paleogene (alternatively Palaeogene) Period is a unit of geologic time that began 66 and ended 23.03 Ma[9] and comprises the first part of the Cenozoic Era. This period consists of the Paleocene, Eocene and Oligocene Epochs.

Paleocene Epoch

Main article: Paleocene

The Paleocene, lasted from 66 million years ago to 56 million years ago.[9]

In many ways, the Paleocene continued processes that had begun during the late Cretaceous Period. During the Paleocene, the continents continued to drift toward their present positions. Supercontinent Laurasia had not yet separated into three continents. Europe and Greenland were still connected. North America and Asia were still intermittently joined by a land bridge, while Greenland and North America were beginning to separate.[41] The Laramide orogeny of the late Cretaceous continued to uplift the Rocky Mountains in the American west, which ended in the succeeding epoch. South and North America remained separated by equatorial seas (they joined during the Neogene); the components of the former southern supercontinent Gondwana continued to split apart, with Africa, South America, Antarctica and Australia pulling away from each other. Africa was heading north toward Europe, slowly closing the Tethys Ocean, and India began its migration to Asia that would lead to a tectonic collision and the formation of the Himalayas.

Eocene Epoch

Main article: Eocene

During the Eocene (56 million years ago - 33.9 million years ago),[9] the continents continued to drift toward their present positions. At the beginning of the period, Australia and Antarctica remained connected, and warm equatorial currents mixed with colder Antarctic waters, distributing the heat around the world and keeping global temperatures high. But when Australia split from the southern continent around 45 Ma, the warm equatorial currents were deflected away from Antarctica, and an isolated cold water channel developed between the two continents. The Antarctic region cooled down, and the ocean surrounding Antarctica began to freeze, sending cold water and ice floes north, reinforcing the cooling. The present pattern of ice ages began about 40 million years ago.[citation needed]

The northern supercontinent of Laurasia began to break up, as Europe, Greenland and North America drifted apart. In western North America, mountain building started in the Eocene, and huge lakes formed in the high flat basins among uplifts. In Europe, the Tethys Sea finally vanished, while the uplift of the Alps isolated its final remnant, the Mediterranean, and created another shallow sea with island archipelagos to the north. Though the North Atlantic was opening, a land connection appears to have remained between North America and Europe since the faunas of the two regions are very similar. India continued its journey away from Africa and began its collision with Asia, creating the Himalayan orogeny.

Oligocene Epoch

Main article: Oligocene

The Oligocene Epoch extends from about 34 million years ago to 23 million years ago.[9] During the Oligocene the continents continued to drift toward their present positions.

Antarctica continued to become more isolated and finally developed a permanent ice cap. Mountain building in western North America continued, and the Alps started to rise in Europe as the African plate continued to push north into the Eurasian plate, isolating the remnants of Tethys Sea. A brief marine incursion marks the early Oligocene in Europe. There appears to have been a land bridge in the early Oligocene between North America and Europe since the faunas of the two regions are very similar. During the Oligocene, South America was finally detached from Antarctica and drifted north toward North America. It also allowed the Antarctic Circumpolar Current to flow, rapidly cooling the continent.

Neogene Period

Main article: Neogene

The Neogene Period is a unit of geologic time starting 23.03 Ma.[9] and ends at 2.588 Ma. The Neogene Period follows the Paleogene Period. The Neogene consists of the Miocene and Pliocene and is followed by the Quaternary Period.

Miocene Epoch

Main article: Miocene

The Miocene extends from about 23.03 to 5.333 Ma.[9]

During the Miocene continents continued to drift toward their present positions. Of the modern geologic features, only the land bridge between South America and North America was absent, the subduction zone along the Pacific Ocean margin of South America caused the rise of the Andes and the southward extension of the Meso-American peninsula. India continued to collide with Asia. The Tethys Seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish-Arabian region between 19 and 12 Ma (ICS 2004). Subsequent uplift of mountains in the western Mediterranean region and a global fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea resulting in the Messinian salinity crisis near the end of the Miocene.

Pliocene Epoch

Main article: Pliocene

The Pliocene extends from 5.333 million years ago to 2.588 million years ago.[9] During the Pliocene continents continued to drift toward their present positions, moving from positions possibly as far as 250 kilometres (155 mi) from their present locations to positions only 70 km from their current locations.

South America became linked to North America through the Isthmus of Panama during the Pliocene, bringing a nearly complete end to South America's distinctive marsupial faunas. The formation of the Isthmus had major consequences on global temperatures, since warm equatorial ocean currents were cut off and an Atlantic cooling cycle began, with cold Arctic and Antarctic waters dropping temperatures in the now-isolated Atlantic Ocean. Africa's collision with Europe formed the Mediterranean Sea, cutting off the remnants of the Tethys Ocean. Sea level changes exposed the land-bridge between Alaska and Asia. Near the end of the Pliocene, about 2.58 million years ago (the start of the Quaternary Period), the current ice age began. The polar regions have since undergone repeated cycles of glaciation and thaw, repeating every 40,000–100,000 years.

Quaternary Period

Main article: Quaternary

Pleistocene Epoch

Main article: Pleistocene

The Pleistocene extends from 2.588 million years ago to 11,700 years before present.[9] The modern continents were essentially at their present positions during the Pleistocene, the plates upon which they sit probably having moved no more than 100 kilometres (62 mi) relative to each other since the beginning of the period.

Holocene Epoch

Main article: Holocene

Current Earth - without water, elevation greatly exaggerated (click/enlarge to "spin" 3D-globe).

The Holocene Epoch began approximately 11,700 calendar years before present[9] and continues to the present. During the Holocene, continental motions have been less than a kilometer.

The last glacial period of the current ice age ended about 10,000 years ago.[42] Ice melt caused world sea levels to rise about 35 metres (115 ft) in the early part of the Holocene. In addition, many areas above about 40 degrees north latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as 180 metres (591 ft) over the late Pleistocene and Holocene, and are still rising today. The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea. Holocene marine fossils are known from Vermont, Quebec, Ontario and Michigan. Other than higher latitude temporary marine incursions associated with glacial depression, Holocene fossils are found primarily in lakebed, floodplain and cave deposits. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likely upthrusting of non-glacial origin. Post-glacial rebound in Scandinavia resulted in the emergence of coastal areas around the Baltic Sea, including much of Finland. The region continues to rise, still causing weak earthquakes across Northern Europe. The equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to near its present boundaries.